I did TASHTEGO''s motor with oxalic acid and one of the little pumps
that works on a drill motor. Two gallons of hot water and a box (1 lb) of powdered oxalic acid from the hardware store. Worked fine. Made the solution in a 5 gallon plastic bucket. Removed the thermostat. Removed the cooling hose from the water pump
and plumbed the drill motor pump
into the inlet. Removed the hose to the exhaust
and plumber back to the bucket. Filled the motor up and let sit for 30 mins. then recycled until outlet was more or less clear. Total of three treatments then flushed with a box of baking soda in 2 gals hot water to neutralize the acid. I did it because I was converting to fresh water cooling using the Indigo kit.